Beam alignment device



Sept 15, 1952 A. w. FRIEND BEAM ALIGNMENT DEVICE 2 SHEETS- SHEET l Filed Feb. 2l, 1951 .h whim.

Patenteri Sept. 16, 1952 BEAIiI ALIGNMEN' DEVCE Albert W. Friend, Princeton, N. J., assigner to Radio Corporation of America, acorporation of Delaware Application February 21, 1951, Serial No. 212,175

6 Claims. l

This invention relates to deflecting yokes for cathode ray tubes, and particularly to defiecting yokes for cathode ray tubes designed to operate in television receivers.

For the purposes of simplicity in explanation, the invention will be described as applied to the defiection yoke of a cathode ray picture tube as used in television apparatus. It will be clear, however, that the invention is equally applicable to yokes for use inother apparatus using cathode ray beam defiecting yokes.

One of the problems facing the designer of apparatus using cathode ray tubes is that of convergence of the electron beam at all points on the plane of the screen of the tube. When the electron beam converges on the screen of the cathode ray tube, it appears as a pin point. When it does not converge on the screen of the cathode ray tube, it appears as a diffused spot of possibly irregular shape whose area is greater than that of a pin point.

In conventional single beam black and White television apparatus, lack of convergence of the electron beam at all points on the screen will result in a picture that is not uniformly focused. The picture will be in focus where the beam converges `on the screen, and somewhat blurred Where the beam converges outside the plane of the screen.

While lack of convergence is objectionable in conventional black and White television receivers using a single electron beam, it is less noticeable than when it occurs in color television receivers using a picture tube having a multi-element screen, wherein the particular colored phosphor energized is dependent upon the angle at which the beam is directed upon the screen. This latter feature is present whether the color receiver uses three separate beams havingdilferent angles of approach or a single beam whose angle of approach is cyclically varied. In such television receivers, lack of convergence of the electron beam or beams at all points on the screen will result not only in a picture that is not uniformly focused, but also in a picture in which undesirable color fringes appear.

It is an object 'of this invention to obtain substantial convergence of the electron beam or beams at all points of the screen of a cathode ray tube.

It is a further object of this invention to provide easily adjustable means to obtain substantial convergence of the electron beam or beams at all points of the screen of a cathode ray tube.

Another object of this invention is to provide means to trim the configuration of the magnetic field inside the defiection yoke of a cathode ray tube.

According to the invention, better convergence of the electron beam or beams of cathode ray tubes at all points on the screen is obtained by trimming the conguration of the magnetic iield inside the deflection yoke. This trimming is accomplished by providing a yoke core whose elements are movable with respect to each other and to the center axis of the yoke, and Whose shape may be altered by moving the said elements. These elements may be segments of a segmented core, or parts of a deformable resilient core.

Other and incidental objects of the invention will be apparent to those skilled in the art from a reading of the following specification and an inspection 0f the accompanying drawings in which:

Figure 1 is a schematic representation of a television system employing an embodiment of the invention;

Figure 2 is a cross section of one type of a defiection yoke constructed in accordance with the invention;

Figure 3 is a cross section along a line 3 3 of the deflection yoke shown in Figure 2;

Figure 4 is a modied form of the deflection yoke shown in Figure 3; and

Figure 5 is a cross section of another type of deflection yoke constructed in accordance With the invention.

Referring to Figure 1 there is shown in block diagram a television arrangement utilizing a three gun tri-color kinescope. Video signals from a conventional black and white television receiver I, are applied simultaneously to three control grids 3a, 3b, and 3c of the three gun kinescope 5. Another signal derived from the video amplifier is used to actuate an automatic color phasing and sampling synchronization circuit 1, which produces a 3.58 mc. sampling wave. The latter is applied through an amplifier tube 9 and appropriate delay lines lla, Il b, and llc to gating tubes |3a, |31), and l3c which supply three sampling pulses, differing in phase by at 3.58 mc., to the three cathodes of the kinescope. Thus, each gun is turned on in time sequence corresponding to the original sampling process at the transmitter, and the beam current from each gun excites only one of the three phosphor colors. The deflection circuitry is of the conventional type, and the kinescope is equipped with a deflection yoke I4 constructed according to the invention. The kinescope is of the type utilizing anapertured mask I5 interposed between the gunsand a dot phosphor screen I1. A color receiver of this type is well known and a full description of its operation is not believed necessary. However, fo-r those who are interested in a more complete description, reference may be had to Gen-- eral Description of Receivers for the RCA Color Television System Which Employs the RCA Di rect View Tri-Color Kinescopes, April 4, 1950, Radio Corporation of America.

Referring to Figure 2, the movable elements ofY the core of the magnetic yoke are segments of a segmented core. These segments, 2Ia,."2lb; and 2 lc, are shown as being-of equal arcrlengthsg, but segments of differing arc lengths could also be used. Secured to a core segment. is.- plate 23 on which is mounted a shaft or plunger 251 Plunger 25 goes through an aperture in the cy*- lindrical housing 21 of the yoke and through a corresponding aperturefin mountingv plate 29, and locking block 3l. The end` of plunger'ZS.; not secured to plate 23 is knurled.

Referring to Figure 3A there is shown. a cross section taken along lines 3f-'33 of` thernagnetic yoke ofFigure 2. The detailsof the locking arrangement are illustrated. A- slot.v 33- is provided onv plunger 25 parallel totY itsi longitudinal axis. A key- 35- engagesthrough locking; block 3i into slot 33. Locking block iiiis-providec1,witli-v a threaded aperture into-which arefengaged. shoe- 33, spring 39; and' screw- 4i.

The plunger 25-can be-movedlY alonglits lungi-- tudinalaxis; radially tothe center of `the-yoke. Key 35 prevents plunger 25 from rotating about its longitudinal axis.. 'DependingV upon the.` position-` ofscrew 4if, shoe ."s'l; exerts.- by; means of, spring 39 aV slight pressure upon plungere 2-5.- to-` hold. it placewhile its position. is: adj/usted,k ori a greater pressure to hold it securely into-place after its nal position 'has been dett-irmined.v

Figure Lit-shows a modification ofthe-y deflectionyoke shown in Figure 3 and in which; thegcore comprises two rings. each, of. which isI out. into segments whose positionsareadjustedin-'the same fashion as the core segments of Figures- 2 and 3. Y

Figure 5 showsanembodiment. oftherinven' tion in which'the movable. elements of, thecore are parts of a deformable resilient 'cor-e; Such a core may be made by mixing neoprene-rubber, vinylite, polyethylene or a similar material. with nely divided ferro-magnetic particles.. This core 43. is provided with a rim 45.- which: engages into a slot at oner extremity of plunger 4-1-and' is held there by means of locking.,v pin '49.. Plunger E1 engages through an aperturein the cylin drical housing 5| of the yoke. vTheother ex tremity of. plunger 4.1 is threaded,.and providedwith a threaded knurled knob.. 5.3i. f

By moving. the coreelements-.relatively to-eachother, the configuration.. of the` magnetic-eldinside the deiiection. yoke can'be changed and adjusted for best; convergence.. In. the embodi mentss'hown in Figures 2", 3,. and.- 4., this, is. ac compli'shed by sliding thev plungers. along; theirlongitudinal' axes,l thereby moving thesegments of the segmented' core. Tn; thefembodi'ment. shown in Figure 5 the same. object'. is. accom.- plishe'd by rotatingl the'threaded. knurled. knobs, about their axes, therebymoving, the plungers along `their longitudinal axes. The shapeV of the deformable core is; altered, and. elements. of the'V 4 core are thus moved with respect to each other and to the center axis of the yoke.

Other modifications of the invention readily suggest themselves. In the embodiments comprising a single ring core, only part of the core elements may be made movable while others may remain fixed. In embodiments comprising a plurality of rings, one ringfmaybemade fixed and unadjustable, while another may be made of movable elements, or of a combination of movable and of fixed elements.

I-IavingV thus described my invention, what is Vclaimed is:

1. A cathodeiray tube deiiection yoke having a plurality: of deecting coils, a magnetic core cradled by saidI deflecting coils, said magnetic coreV comprising a. plurality of elements, and means to move one of said elements along a radius from the center aXis of said yoke.

2. A cathode ray tube. deflection yoke having a: plurality of deilecting coils,A a. magnetic core cradled' by said--deflecting coils, said magnetic core comprising-'-afpluralityof segments, and. means to move one of Said` segments-along: a

\ radius'. from Vthe center axisiof said yoke;

3. A cathode raytube deflection yokehaving a plurality of deilecting coils, a. magnetic corer cradled by Vsaiddeiiecting coils and comprising a plurality of ring soneofsaid rings comprising a plurality ofsegments, and means. to move-se.- lectively said segments along a radius fromthe center. axis of said yoke.

- 4. A cathode ray tube deilecti'on-yokehavingT a pluralityot deflectingr coils a magnetic. corecradled by said deilecting-A coils, said magnetic kcore comprisinga plurality of` elements, and. a. Vshaft attached to at least one, of said elementsV -whercbysaid element maybe movedf along a'.

a plurality of deflection coils, a magnetic core cradled by said deflection coils, said magnetic core: comprising. a pluralityof elements; a. shaft attached to atleast one-of said: elements'whereby. said element vmay be Lmoved along a radius from-the center axis of saidyoke, and lookin means to, lock said-shaft into position. f`

- ALBERT W.

aggressore. CITED.

The'. following references are; ofrecord the:

file of? this pateiitr. 1

' Y uitrit-:i3-v sTarEsP-A'rEN'r-s" Number 50i-,esi frreas Britain- T. Mar. s, 1939- 

